The sequence of morphological changes which characterize Caulobacter development are principally expressed as alterations of the cell envelope and appendant structures. These changes occur at specific times in the cell cycle and at specific cellular locations. The objective of this study is the temporal and spatial organization of Caulobacter development. The proposal sets forth two primary areas of investigation: 1) Regulation of Specific Cell Surface Structures: Flagella, pili and stalked cell membrane proteins are synthesized or assembled into supramolecular structures at specific times in the Caulobacter cell cycle. Because their assembly sites are strictly defined in the Caulobater cell surface, the biogenesis of these structures must also involve their synthesis at and/or translocation to specific cellular locations. The regulation of expression of these site-specific structures will be studied with the consideration that the cell membrane may potentially determine these compartments through specific nucleic acid-cell envelope interactions. 2) Analysis of the Caulobacter Cell Envelope: Studies aimed at defining specific membrane components, such as those responsible for polar phage adsorption, will include a general description of the membrane as necessary for understanding morphological and biochemical alterations which occur either during normal development or as a function of genetic alteration. Particular emphasis will be placed on the identification and characterization of components which are unique to this bacterial membrane and/or differentially expressed during the cell cycle. These studies should provide important information concerning selective gene expression, synthesis and insertion of proteins in the cell membrane, and assembly of supramolecular structures associated with the cell envelope. Understanding the molecular biology of polarity as expressed in this simple system is also likely to have significance and applicability to fundamental problems of developmental biology.